In the late 1960s, Phillips was hired by Sid Gillman to serve as a defensive assistant coach for the San Diego Chargers. In 1973, Gillman became head coach of the Houston Oilers, and he brought Phillips with him as his defensive coordinator.

In 1975, Phillips was named head coach and general manager of the Oilers, and he served in that capacity through 1980.[1] As coach of the Oilers, he became the winningest coach in franchise history (59-38 record). He was known for his trademark cowboy hat on the sidelines, except when the Oilers played in the Astrodome or other domed stadiums. He stated that his mother taught him not to wear a hat indoors; his former boss Bear Bryant similarly refused to wear his trademark fedora during indoor games.[2] Under Phillips, the Oilers reached the AFC Championship Game in two consecutive seasons, losing to the Super Bowl champion Pittsburgh Steelers 34-5 in 1978 and 27-13 in 1979. Both teams were members of the competitive AFC Central Division and thus played three times in both 1978 and 1979, fueling an intense rivalry. During this period of league-wide AFC dominance, some commentators considered the Oilers and Steelers to be the two best teams in the NFL. Phillips remarked at the time, "The road to the Super Bowl goes through Pittsburgh."

From 1981 through the first 12 games of the 1985 season, he was the head coach of the New Orleans Saints, and as in his coaching tenure with the Oilers, Phillips took off his trademark Stetson inside the Louisiana Superdome. In 1983, his Saints almost had the first winning season and playoff berth in franchise history. The Rams beat the Saints for the final playoff spot in week 16, 26-24 on Mike Lansford's 42-yard field goal with 00:02 to play.

Phillips resigned as Saints coach on November 25, 1985, one day after a 30-24 victory over the Minnesota Vikings.

Phillips later worked as a football color analyst for television and radio. He subsequently retired to his horse ranch in Goliad, Texas.

Phillips endorsed his own brand of sausages and also served as the spokesman for Spectrum Scoreboards. Bum was also a spokesman for Texas State Optical (TSO), a regional chain of prescription eyewear retailers, during part of the '90s. He was also a spokesman for Hearing Aid Express, a Texas-based hearing aid company, from 2001 until his death, as well as a spokesman for Blue Ribbon Sausage beginning in 1986.

His son, Wade Phillips, has also held assistant and head coaching jobs in the NFL and was the head coach of the Dallas Cowboys from February 2007 to November 2010. Wade was hired by the Houston Texans on January 5, 2011, as their new defensive coordinator almost exactly 30 years after his father was terminated by Oilers owner Bud Adams on December 28, 1980, after the Oilers failed to advance past the first round of the playoffs.

In 2010, he published his memoirs, Bum Phillips: Coach, Cowboy, Christian.

Phillips died at his ranch in Goliad, Texas, on October 18, 2013, at the age of 90. He was survived by his second wife, Debbie, and six children from his first marriage along with almost two dozen grandchildren. The cause wasn't given.[3] Tennessee Titans owner Bud Adams died just three days after Phillips did. In honor of him coaching both Nederland HS and PNG HS, the rivalry will now be named the Bum Phillips Bowl.

"There's two kinds of coaches, them that's fired and them that's gonna be fired."[4]

"I always thought I could coach. I just thought people were poor judges of good coaches."[5]

"I've never seen a hammer and tong game like that one."

To a reporter who said, "He sure gets up slow", after Earl Campbell had been tackled. "Yes, but he goes down slow, too."

"The harder we played the behinder we got."

"Mama always said that if it can't rain on you, you're indoors." (Explaining why he wouldn't wear his cowboy hat in the Astrodome, the first domed stadium)

"Dallas Cowboys may be America's team, but the Houston Oilers are Texas' team."

"I never scrimmage Oilers against Oilers... what for? Houston isn't on our schedule." (Source: The Book of Sports Lists)

(To an official) "Hey, can I, can I tell you one thing? That's three holding penalties on one football team in a quarter and a half. (Pauses) That ain't funny."

(To an official) "Now, you can't do that! If you do it, I'm telling you you'll have more hell over it than a little bit."

(after playing the Steelers for the fifth time in two seasons and planning to meet them a sixth time) "The road to the Super Bowl runs through Pittsburgh, sooner or later you've got to go to Pittsburgh.[6]

(20 years after playing Pittsburgh six times in two seasons) "Don't take long to spend all the time you want in Pittsburgh."[7]

(referring to Miami Dolphins coach Don Shula) "He can take his'n and beat your'n and take your'n and beat his'n."[8] He also said the same line about Bear Bryant.[9]

(referring to Houston Oilers quarterback Warren Moon) "That boy could throw a football through a car wash and not get it wet."

(when asked about Oilers RB Earl Campbell's inability to finish a one-mile run in training camp) "When it's first and a mile, I won't give it to him."

(when asked by Bob Costas why he took his wife on all of the Oilers' road trips) "Because she's too ugly to kiss goodbye."[10]

(on January 7, 1980, to the crowd at the Astrodome that welcomed the Oilers home after their second consecutive loss to the Steelers in the AFC championship game) "One year ago, we knocked on the door. This year, we beat on the door. Next year, we're going to kick the son of a bitch in."[11][12][13]

(of Earl Campbell) "I don't know if he's in a class by himself, but I do know that when that class gets together, it sure don't take long to call the roll."[14]

Late one night, Phillips and Sid Gillman were watching film and Phillips began to doze off. Gillman woke him up by saying, "Hey Bum, this is better than making love." Phillips responded, "Either I don't know how to watch film, Sid, or you don't know how to make love." (Phillips later indicated that his language may have actually been stronger than that.)[15]